Although the amount of oxygen evolution electrocatalyst is a factor determining its efficiency, its fundamental correlation with activity remains unclear. To address this issue, we take advantage of a urea-based chemical bath deposition method (CBD) that enables to control the amount of electrocatalyst (Fe(OH)₂ and α-Co(OH)₂) deposited on conducting glass. The thickness of the resulting films, whose use in electrocatalysis is unprecedented, is tuned by controlling the deposition time. The turnover frequency (TOF) for O₂ generation decreases drastically as the electrocatalyst amount increases from equivalent coverages of 3.5 monolayers (ML) for Fe(OH)₂ and of 0.06 ML for α-Co(OH)₂ electrodes. The contrasting behavior of both hydroxides comes from the different structure of the incipient deposits, formed by small acicular nanoparticles in the case of Fe(OH)₂ and larger flat microparticles in the case of α-Co(OH)₂. The former structure allows a large fraction of the Fe sites to be in direct contact with solution, while such a fraction rapidly diminishes with loading for α-Co(OH)₂. In addition, the resulting Co(OH)₂ electrodes show TOFs similar or higher than those of electrodes prepared by more complex routes. The optimum ultrathin films are remarkably stable in alkaline media, showing that the preparation of efficient electrocatalysts for oxygen evolution with an extremely small amount of metal through a novel, facile and scalable CBD is possible.

尽管析氧电催化剂的量是决定其效率的因素，但其与活性的基本相关性仍不清楚。为了解决此问题，我们利用了基于尿素的化学浴沉积方法（CBD），该方法能够控制沉积在导电玻璃上的电催化剂（Fe（OH）₂和α- Co（OH）₂）的量。通过控制沉积时间可以调节所得到的膜的厚度，该膜在电催化中的应用是空前的。随着电催化剂用量的增加，Fe（OH）_2的单层覆盖量为3.5单层（ML），α- Co（OH）的单层覆盖量为0.06 ML，O ₂生成的周转频率（TOF）急剧降低。_2个电极。两种氢氧化物的对比行为来自初始沉积物的不同结构，在Fe（OH）₂的情况下由针状小颗粒形成，而在α- Co（OH）₂的情况下由较大的扁平颗粒形成。前者的结构允许大部分Fe位点直接与溶液接触，而随着α- Co（OH）_2的负载，这种位点会迅速减少。另外，所得的Co（OH）₂电极显示的TOF与通过更复杂的路线制备的电极相似或更高。最佳的超薄薄膜在碱性介质中具有显着的稳定性，这表明可以通过新颖，便捷且可扩展的CBD用极少量的金属制备高效的氧气析出电催化剂。